Abundances of intertidal macro-species measured through a multi-factorial in situ experiment of 10 weeks in a eelgrass bed in St. Lawrence Estuary (Baie-Saint-Ludger, Canada)

We evaluated single and interactive effects of density reduction of Zostera marina L., a habitat-forming species, shading, and sediment nutrient enrichment on the response of intertidal epibenthic macro-species abundances. Abundances were measured two weeks after reducing eelgrass density (Period T1), then nutrients were added to the sediments and shades were added above the bed. Abundances were measured three weeks later (Period T2), then shades were taken down. Final abundances were measured five weeks later (Period T3). Epibenthos was collected using mesh bags (mesh size of 500 µm, diameter about 18 cm), each individual collected was identified then sifted through a series of sieves as a proxy for biomass (ash free dry weight; AFDW).